r compulsion, can have no
effect on his right to object to the jurisdiction. If this were not
so, the condition of the two parties would be grossly unequal. For if
a plea to the jurisdiction were ruled against the plaintiff, he could
at once take his writ of error, and have the ruling reviewed here;
while, if the same plea were ruled against the defendant, he must not
only wait for a final judgment, but could in no event have the ruling
of the Circuit Court upon the plea reviewed by this court. I know of
no ground for saying that the laws of the United States have thus
discriminated between the parties to a suit in its courts.

It is further objected, that as the judgment of the Circuit Court was
in favor of the defendant, and the writ of error in this cause was
sued out by the plaintiff, the defendant is not in a condition to
assign any error in the record, and therefore this court is precluded
from considering the question whether the Circuit Court had
jurisdiction.

The practice of this court does not require a technical assignment of
errors. (See the rule.) Upon a writ of error, the whole record is open
for inspection; and if any error be found in it, the judgment is
reversed. (Bank of U.S. _v._ Smith, 11 Wheat., 171.)

It is true, as a general rule, that the court will not allow a party
to rely on anything as cause for reversing a judgment, which was for
his advantage. In this, we follow an ancient rule of the common law.
But so careful was that law of the preservation of the course of its
courts, that it made an exception out of that general rule, and
allowed a party to assign for error that which was for his advantage,
if it were a departure by the court itself from its settled course of
procedure. The cases on this subject are collected in Bac. Ab., Error
H. 4. And this court followed this practice in Capron _v._ Van
Noorden, (2 Cranch, 126,) where the plaintiff below procured the
reversal of a judgment for the defendant, on the ground that the
plaintiff's allegations of citizenship had not shown jurisdiction.

But it is not necessary to determine whether the defendant can be
allowed to assign want of jurisdiction as an error in a judgment in
his own favor. The true question is, not what either of the parties
may be allowed to do, but whether this court will affirm or reverse a
judgment of the Circuit Court on the merits, when it appears on the
record, by a plea to the jurisdiction, that it is a case to whic